Recent interest in microbial production of fuels was bolstered by synthesis of a variety of “next-generation” fuels with improved properties (Atsumi, 2008). Shen, et al. (2010) Appl. Environ Microbiol; Tseng, et al. (2012) PNAS; Bond-Watts, et al. (2011) Nat. Chem. Biol.; Withers, et al. (2007) Appl. Environ. Microbiol.). Most “next generation” fuel targets are either C5 or smaller alcohols or long chain fatty acids/methyl esters. While longer chain acids or isoprenoid derived fuels may serve as potential biodiesel or jet fuels, gasoline alternatives for spark ignition engines would preferably fall in the C6-C7 range. Such medium-chain length alcohols achieve energy density equal to that of petroleum derived gasoline with reduced costs of downstream separation. Branched alcohols have the additional property of improved octane rating (Huang, et al. (2011) Energy and Environ. Sci.; Dugar, et al. (2011) Nat. Biotech.).